This invention relates generally to a workholding chuck assembly for use in high speed machining applications, and more specifically to a sliding jaw chuck assembly including a plurality of radially positionable master slides having a jaw support located at one end of each master slide and a counter balance located at the opposite end therefrom. A centrally-located axially-movable draw spool is operably coupled to each master slide by a lever such that the lever rocks about a pin as the draw spool moves to position the jaw supports radially inwardly and outwardly. The invention further provides a sealed assembly which prevents entry of debris into the chuck cavity and provides a self-lubricating assembly.
Chucks of the type to which this invention is directed include a number of internal moving parts which serve to open and close the gripping jaws. The smooth operation of these parts is most important to assure that there is a positive clamping of the workpiece when the jaws are closed, and further that each of the jaws applies equal pressure against the workpiece to prevent distortion and possible eccentric location of the workpiece.
There has been a recent trend to require sliding jaw chucks to operate at significantly higher rotational speeds. As such, the rotational balance of the chuck and the workpiece held within the chuck become increasingly important. At the speeds at which many chucks are used in modern manufacturing processes, even slight eccentricities or out of balance is unwanted. For example, an imbalance may cause improper machining requiring rejection of the workpiece. Alternately, an imbalance may create a change in the grip force as a result of the centrifugal force created by the rotation of the jaw supports. Thus, it is desirable to provide a chuck which maintains a proper balance and constant gripping force independent of rotational speed and which is readily adjustable to ensure concentric alignment with the machine tool.
Conventional sliding jaw chucks do not provide a completely sealed environment for the sliding jaw assembly. As such, debris may enter the chuck cavity causing faulty operation and an increased frequency of maintenance. Furthermore, it is difficult to assure lubrication of all critical points in the chuck actuating system. Thus, it is desirable to provide a chuck having a closed, oil-filled cavity.
The present invention provides a fully-sealed, self-lubricating closed center countercentrifugal sliding jaw chuck assembly for use in either ID or OD chucking applications. The chuck assembly includes a sealed housing and a sliding jaw assembly having a plurality of master slides supported in the housing for radial positioning. Each of the master slides has a jaw support formed on one end and a counterweight support formed on the opposite end. The counterweights function to generate centrifugal forces equal in magnitude but opposite in direction to the centrifugal forces associated with jaw mechanism. A draw spool is operably coupled to the master slide through a pivoting lever assembly which radially positions the master slides in response to axial movement of the draw spool. A plurality of the slide covers are disposed over the jaw support to maintain a lubricant tight seal, while adapting the chuck assembly to receive a variety of gripping jaw such that the chuck assembly of the present invention may be readily adaptable for a wide range of applications.